22 research outputs found
X-ray synchrotron emission from the oblique shock in the jet of the powerful radio galaxy 3C 346
We report the first detection, with Chandra, of X-ray emission from the jet
of the powerful narrow-line radio galaxy 3C 346. X-rays are detected from the
bright radio and optical knot at which the jet apparently bends by about 70
degrees. The Chandra observation also reveals a bright galaxy-scale atmosphere
within the previously-known cluster, and provides a good X-ray spectrum for the
bright core of 3C 346. The X-ray emission from the knot is synchrotron
radiation, as seen in lower-power sources. In common with these sources, there
is evidence of morphological differences between the radio/optical and X-ray
structures, and the spectrum is inconsistent with a one-component
continuous-injection model. We suggest that the X-ray-bright knot is associated
with a strong oblique shock in a moderately relativistic, light jet, at about
20 degrees to the line of sight, and that this shock is caused by the jet
interacting with the wake in the cluster medium behind 3C 346's companion
galaxy. The general jet curvature can result from pressure gradients in the
cluster atmosphere.Comment: Accepted for publication in the MNRAS. 9 page
The inner jet of radio galaxy NGC 315 as observed with Chandra and the VLA
We present Chandra X-ray results for the jet, nucleus, and gaseous atmosphere
of NGC 315, a nearby radio galaxy whose jet kinematics are known through deep
radio mapping. Diffuse X-ray synchrotron emission is detected from the jet out
to 30 arcsec from the nucleus, through regions both of fast bulk flow and
deceleration. The X-ray to radio flux ratio drops considerably where the flow
decelerates, but the X-ray and radio emissions show similar transverse extents
throughout, requiring distributed particle acceleration to maintain the supply
of X-ray-emitting electrons. A remarkable knotty filament within the jet is
seen in both the radio and X-ray, contributing roughly 10 per cent of the
diffuse emission along its extent at both wavelengths. No completely
satisfactory explanation for the filament is found, though its oscillatory
appearance, roughly aligned magnetic field, and requirements for particle
acceleration, suggest that it is a magnetic strand within a shear layer between
fast inner and slower outer flow.Comment: Accepted for publication in the MNRAS. 13 pages,14 figures (some in
colour
A relativistic model of the radio jets in NGC 315
We apply our intrinsically symmetrical, decelerating relativistic jet model
to deep VLA imaging of the inner 140 arcsec of the giant low-luminosity radio
galaxy NGC 315. An optimized model accurately fits the data in both total
intensity and linear polarization. We infer that the velocity, emissivity and
field structure in NGC 315 are very similar to those of the other
low-luminosity sources we have modelled, but that all of the physical scales
are larger by a factor of about 5. We derive an inclination to the line of
sight of 38 degrees for the jets. Where they first brighten, their on-axis
velocity is approximately v/c = 0.9. They decelerate to v/c = 0.4 between 8 and
18 kpc from the nucleus and the velocity thereafter remains constant. The speed
at the edge of the jet is roughly 0.6 of the on-axis value where it is best
constrained, but the transverse velocity profile may deviate systematically
from the Gaussian form we assume. The proper emissivity profile is split into
three power-law regions separated by shorter transition zones. In the first of
these, at 3 kpc (the flaring point) the jets expand rapidly at constant
emissivity, leading to a large increase in the observed brightness on the
approaching side. At 10 kpc, the emissivity drops abruptly by a factor of 2.
Where the jets are well resolved their rest-frame emission is
centre-brightened. The magnetic field is modelled as random on small scales but
anisotropic and we rule out a globally ordered helical configuration. To a
first approximation, the field evolves from a mixture of longitudinal and
toroidal components to predominantly toroidal, but it also shows variations in
structure along and across the jets, with a significant radial component in
places. Simple adiabatic models fail to fit the emissivity variations.Comment: 20 pages, 17 figures, MNRAS (in press
Is cold gas fuelling the radio galaxy NGC 315?
We present WSRT, VLA and VLBI observations of the HI absorption in the radio
galaxy NGC 315. The main result is that two HI absorbing systems are detected
against the central region. In addition to the known highly redshifted, very
narrow component, we detect relatively broad (FWZI 150 km/s) absorption. This
broad component is redshifted by ~80 km/s compared to the systemic velocity,
while the narrow absorption is redshifted ~ 490 km/s. Both HI absorption
components are spatially resolved at the pc-scale of the VLBI observations. The
broad component shows strong gradients in density (or excitation) and velocity
along the jet. We conclude that this gas is physically close to the AGN,
although the nature of the gas resulting in the broad absorption is not
completely clear. The possibility that it is entrained by the radio jet appears
unlikely. Gas located in a thick circum-nuclear toroidal structure cannot be
completely ruled out although it appears difficult to reconcile with the
observed morphology and kinematics of the HI. A perhaps more likely scenario is
that the gas producing the broad absorption could be (directly or indirectly)
connected with the fuelling of the AGN, i.e. gas that is falling into the
nucleus. If this is the case, the accretion rate derived is similar to that
found for other X-ray luminous elliptical galaxies, although lower than that
derived from the radio core luminosity for NGC 315. The density distribution of
the narrow component is, featureless. Moreover, we detect a small amount of HI
in emission a few kpc SW of the AGN, coincident with faint optical absorption
features and at velocities very similar to the narrow absorption. This suggests
that the gas causing the narrow absorption is not close to the AGN and is more
likely caused by clouds falling into NGC 315.Comment: Accepted for publication in A&A, 9 pages, 6 figure
Growth, profits and technological choice: The case of the Lancashire cotton textile industry
Using Lancashire textile industry company case studies and financial records, mainly from the period just before the First World War, the processes of growth and decline are re-examined. These are considered by reference to the nature of Lancashire entrepreneurship and the impact on technological choice. Capital accumulation, associated wealth distributions and the character of Lancashire business organisation were sybiotically linked to the success of the industry before 1914. However, the legacy of that accumulation in later decades, chronic overcapacity, formed a barrier to reconstruction and enhanced the preciptious decline of a once great industry
Discharge and nutrient uncertainty: implications for nutrient flux estimation in small streams
Kinematics of the parsec-scale radio jet in 3C 48
âThe definitive version is available at www3.interscience.wiley.com '. Copyright Royal Astronomical SocietyWe present results on the compact steep-spectrum quasar 3C 48 from observations with the Very Long Baseline Array (VLBA), the Multi-Element Radio Linked Interferometer Network (MERLIN) and the European Very long baseline interferometry (VLBI) Network (EVN) at multiple radio frequencies. In the 1.5-GHz VLBI images, the radio jet is characterized by a series of bright knots. The active nucleus is embedded in the southernmost VLBI component A, which is further resolved into two sub-components A1 and A2 at 4.8 and 8.3 GHz, respectively. A1 shows a flat spectrum and A2 shows a steep spectrum. The most strongly polarized VLBI components are located at component C ⌠0.25 arcsec north of the core, where the jet starts to bend to the north-east. The polarization angles at C show gradual changes across the jet width at all observed frequencies, indicative of a gradient in the emission-weighted intrinsic polarization angle across the jet and possibly a systematic gradient in the rotation measure; moreover, the percentage of polarization increases near the curvature at C, likely consistent with the presence of a local jetâinterstellar-medium interaction and/or changing magnetic-field directions. The hot spot B shows a higher rotation measure, and has no detected proper motion. These facts provide some evidence for a stationary shock in the vicinity of B. Comparison of the present VLBI observations with those made 8.43 yr ago suggests a significant northward motion for A2 with an apparent transverse velocity ÎČapp= 3.7 ± 0.4c . The apparent superluminal motion suggests that the relativistic jet plasma moves at a velocity of âł0.96c if the jet is viewed at an inclination angle less than 20° . A simple precessing jet model and a hydrodynamical isothermal jet model with helical-mode KelvinâHelmholtz instabilities are used to fit the oscillatory jet trajectory of 3C 48 defined by the bright knotsPeer reviewe
Toward a global perspective of family continuity: The effects of international exchange on child welfare practice programs and policy
Poor aspirin response in diabetic patients presenting with acute coronary syndromes: Results using a near patient test.
Epub ahead of prin
Individualised assessment of response to clopidogrel in patients presenting with acute coronary syndromes: a role for short thrombelastography?
Introduction: There is considerable interindividual variation in response to the antiplatelet agent clopidogrel. Hyporesponse predicts negative outcomes in patients presenting with a variety of ischemic cardiac conditions and following intracoronary stent placement. Many tests of clopidogrel activity are time consuming and complex. Short thromboelastography (s-TEG) allows rapid measurement of platelet clopidogrel response. Aims: We initiated this study to investigate the utility of s-TEG in assessing the response to clopidogrel in patients presenting with acute coronary syndromes (ACS) and to compare these results with established clopidogrel monitoring techniques. Methods: Patients admitted with unstable angina (UA) or Non ST elevation myocardial infarction (NSTEMI) undergoing coronary angiography were recruited. After routine loading with clopidogrel, all patients were tested with s-TEG and Accumetrics Verify-Now rapid platelet function analyzer (VN-RPFA). We used the modified TEG technique of measuring area under the curve at 15 min (AUC15), which allows a rapid estimation of antiplatelet response. Vasodilator-stimulated phosphoprotein phosphorylation (VASP) was also tested in a subgroup of patients. Clinical follow-up was obtained at 1 year. s-TEG results were correlated with VN-RPFA and VASP findings. Results: A total of 49 patients (33 male, mean age 63) were recruited and tested with s-TEG and VN-RPFA and a total of 39 patients were also assessed with VASP. s-TEG readings correlated well with VN-RPFA (r2= 0.54, P < 0.0001) and VASP (r2= 0.26, P= 0.001). Conclusion: s-TEG provides timely results which compare to current tests of clopidogrel activity. This technique can also be used to measure a variety of other clotting parameters and as such could develop into a valuable near patient test for the interventional cardiologist